Electrodeposition



Patented Apr. 2, 1940 UNITED STATES PATENT OFFICE ELECTEODEPOSITION No Drawing.

Application July 31, 1936,

Serial No. 98,719

23 Claims.

This invention relates to improvements in electrodeposition. It relates particularly to improved electrolytic baths and methods of electrodepositing metals from such baths.

This application is a continuation-in-part of my applications Serial Nos. 691,081 and 691,082, filed September 26, 1933, and Serial No. 737,777, filed July 31, 1934.

It has been found, according to the present invention, that improved results are secured in the electrodeposition of metals by having present in the electrolytic bath a nuclear alkyl derivative of an aromatic sulfonic acid of the benzene series (as distinguished from nuclear alkyl derivatives of condensed polynuclear aromatic sulfonic acids, such as, those of the naphthalene series) containing at least 7 carbon atoms in an alkyl group and which group is preferably an openchain aliphatic hydrocarbon radical containing at least 10 carbon atoms. (As employed herein, the term nuclear refers to substituents for hydrogen atoms in the aromatic nucleus.) Thus, it has been found that the presence of a small amount of an alkyl aromatic sulfonate of the type herein disclosed eliminates pitting and forma tion of pin-holes, and results in bright, uniform deposits of metal. Alkyl aromatic sulfonates of the type herein disclosed have the further advantages of acting as emulsifying agents and of forming soluble salts with many of the metals employed in electro-plating.

The aromatic nuclei of said alkyl aromatic sulfonic acid compounds may be free from further substituents or they may contain one or more substituents, as for example, -OH, alkyl, aryl, alkcxy, aryloxy, and/or carboxyl (in the free acid or salt form).

Alkyl aromatic sulfonic acid compounds which correspond with the general formula in which X represents hydrogen, ahydroxyl group, a lower alkyl group, an alkoxy group (e. g., methoxy, ethoxy, benzyloxy, etc.), an aryloxy group (e. g., phenoxy, etc.), or a carboxyl group, R represents an alkyl hydrocarbon radical (saturated or unsaturated) 7 containing 10 or more (preferably 10 to 19) carbon atoms, and M represents hydrogen or a metal, or an ammonium or an organic ammonium radical, constitute an especially useful class of agents for improvingthe elecrodeposition of metals in accordance with the present invention. For convenience, they will be hereinafter referred to as "alkyl aromatic sulfonates of the benzene series which term generically includes the said derivatives, whether in the form of the free sulfonic acids or their salts. employed in accordance with the present invention are those in which the alkyl group contains a branched carbon chain, whether linked to the benzene nucleus by an end carbon atom (an alpha carbon atom) or an intermediate carbon atom (that is, whether a primary, secondary or tertiary alkyl group).

Preferred compounds employed in accordance with the present invention are the mixed alkyl derivatives of aromatic sulfonic acids of the benzene series (e. g.. those derived from benzene, phenol, cresols, phenetol, etc.) in which the alkyl groups correspond with the aliphatic hydrocarbons of petroleum distillates and similar products boiling above 170 0., and which are obtainable by halogenation of a petroleum distillate or similar product, and especially of an allphatic hydrocarbon mixture of the Pennsylvania petroleum kerosene type of which at least 80 per cent boils above 170 C., followed by condensation of resulting mixed alkyl halides with an aromatic compound, preferably with the aid of a metal halide condensing agent, and sulfonation of resulting mixed alkyl derivatives of the aromatic compound. Alkyl aromatic sulfonates of the type employed in accordance with the present invention, and methods of preparing them are claimed in my application Serial Nos. 691,081 and 691,082, filed September 26, 1933; Serial No. 737,777, filed July 31, .1934; and Serial No. 93,521, filed July 30, 1986.

This invention includes the use of the free sulfonic acids and various salts of the said sulfonic acids in which the hydrogen of the sulfo or other acidic groups is replaced by an inorganic or organic salt-forming radical. Among the more easily procured salts are the ammonium, alkalimetal, alkaline earth metal salts and the salts in which the acidic groups are neutralized by the more common organic bases, such as mono-, di-, or triethanolamine, pyridine, ethylene diamine, amylamines, triethylene tetramine, etc. If the salt-forming basic component is polybasic, it may be neutralized in part with the above defined sulfonic acids and in part by other suitable acidic materials. For specific uses the sulfonates are advantageously employed in the form of the salt of the metal to be deposited.

The following examples illustrate several meth- The alkyl aromatic sulfonates preferably ods of preparing alkyl aromatic sulfonates useful in connection with the present invention. It will be evident from a consideration of the disclosure herein that the invention is not limited to the use of products prepared in this manner but includes products of the type referred to herein when prepared in other ways. The parts are by weight and temperatures are in degrees centigrade.

EXAMPLE 1 Part 1.--Ch10rine is passed into 400 parts of a kerosene boiling from about 195 to about 300 (and boiling for the most part from about 225 to 275), having a specific gravity of 0.799 at 24, containing about 5.6 per cent of unsaturated hydrocarbons, and having a probable carbon content ranging from 11 to 18 carbon atoms and a probable average content of about 13.4 carbon atoms, at 50 in diffused light until the reaction mixture reaches a specific gravity of 0.91. There is an increase of weight of 81 parts, 2 parts of which is due to dissolved hydrogen chloride. The resulting product comprises unchlorinated hydrocarbon in admixture with mono-, di-, and polychlorinated hydrocarbons, the average chlorine content of the mixture being equivalent to about one and one-tenth atoms of chlorine per molecule of hydrocarbon having the stated carbon content. 150 parts of this chlorinated mixture is slowly added to an agitated mixture of 200 parts phenol and 5 parts anhydrous zinc chloride at 75, and the temperature is maintained at 75 for about 30 minutes after all the chlorinated mixture has been added. The temperature of the mixture is then raised and maintained at for 2.5 hours. 5 parts of zinc dust is then added, and after one hour another 5 parts of zinc dust is added, the temperature being maintained during this addition and for about 3 hours afterward at 135. The reaction mixture is cooled, treated withwater, and the oil is separated from the water and residual zinc dust and fractionally distilled. The fraction boiling from to 250 at 4 mm. pressure is separately collected. It comprises a mixture of saturated and unsaturated alkyl phenols and chloralkyl phenols.

Part 2.The crude oil thus obtained in Part 1 of this example is fractionally distilled in vacuo and the distillate boiling from to 225 at 4 mm. pressure is separately collected. To 25 parts of this distillate, under agitation and maintained at a temperature of 30, there is slowly added 11.6 parts'of chlorsulfonic acid. The mixture is agitated for 15 minutes after all of.the chlorsulfonic acid has been added. The temperature of the mixture is then raised and held at 70 for 15 minutes. The mixture is then drowned in 250 parts of water, the solution is made neutral to Brilliant Yellow and Congo Red papers by addition of caustic soda thereto, and evaporated to dryness on a double drum drier. The resulting product comprises the sodium salts of a mixture of alkyl phenol sulfonic acids in which the alkyl groups contain probably 11 to 18 carbon atoms. It is a light colored to White powder substantially free (less than 4 per cent) of inorganic salts.

EXAMPLE 2 Part 1.-A kerosene fraction which distilled between and 295 was chlorinated with chlorine gas, in the presence of a small amount of iodine as a catalyst and at a temperature near 50, until the chlorinated mixture had increased about 18 per cent in Weight because of organically combined chlorine, and exclusive of hydrogen chloride dissolved in the mixture. From the boiling range of the kerosene fraction it was deduced that the average molecular carbon content of the hydrocarbons in the kerosene fraction was between 13 and 14 carbon atoms, and the organically-combined chlorine in the chlorinated mixture was equivalent to about 100 per cent of monochlorination of the said hydrocarbons.

A mixture of 100 parts of the resulting chlorinated kerosene mixture, 50 parts of phenol, and 5 parts of anhydrous zinc chloride was charged to a suitable vessel fitted with a mechanical agitator and a reflux condenser. The agitated mixture was gradually heated to a temperature of 133 to 137 and held at that temperature for about 5 hours. Thereafter, it was allowed to settle; the upper oily liquid portion was decanted into a 10 per cent brine solution and washed with small amounts of brine until it was acid free. The washed oil was distilled in vacuo. and the fraction distilling over between 128 at 10 mm. and 225 at 10 mm. was collected separately. The distilled oil thus obtained was chiefly a mix-- ture of nuclearly alkylated phenols in which the nuclearly substituted hydrocarbon residues are derived from the chlorinated kerosene.

Part 2.-100 parts of the mixture of alkylated phenols obtained in Part 1 of this example and 31 parts of 50 per cent aqueous caustic soda were mixed in a suitable vessel fitted with agitator and reflux condenser. The mixture was heated slowly to about 100 and 30 parts of diethyl sulfate were then introduced as a continual but uniform stream, extended over a period of about one hour. The mixture was then heated to about 150 and stirred under reflux at that temperature for about 3 hours. The mass was then cooled to 100, poured into water, filtered, and after a period of settling, the upper layer of oil was separated and distilled in vacuo. The fraction which distilled between 120 at 5 mm. and 190 at 5 mm. was collected separately, as a pale yellow mobile oil which is soluble in carbon tetrachloride. ethylene dichloride, benzene, ethyl ether, etc.

Part 3.-15 parts of the distilled mixture of alkyl phenetols obtained in Part 2 of this example were cooled to a temperature between 0 and 5, and while the mixture was rapidly agitated, 28 parts of. sulfuric acid monohydrate were added slowly to it. During the acid addition, the temperature of the sulfonation mass was maintained below 15. The mixture was agitated at room temperature for about 1 hour until a sample, when neutralized with caustic soda, was completely soluble in about 20 to 25 times the samples weight of water. The mass was then diluted with about 100 parts of an ice and water mixture, carefully neutralized to faint alkalinity with aqueous caustic soda, and the neutral solution was evaporated to dryness. The final product was chiefly a mixture containing the sodium sulfonates of alkyl phenetols.

EXAMPLE 3 100 parts of commercial lauryl ,alcohol (obtained by hydrogenation of fatty acids from cocoanut oil), 100 parts of phenol, and 100 parts of anhydrous zinc chloride are mixed and refiuxed at 190 to 200 with agitation for about 16 hours. The condensation product is washed with water until practically free of water-soluble products, and the resulting oil is fractionally distilled in vacuo. The fraction of the distillate collected as a faint yellow to water-white oil between 210 to 230 at 13 mm. mercury pressure 122 parts of chlorsulfonic acid are added to 270 parts of the resulting oil which is held at a temperature below 10, then sulfonation is continued at room temperature for 2 hours. The sulfonation mixture is drowned in four times its weight of a mixture of ice and water and a solution of sodium hydroxide is added while keeping the temperature below 35 until the product is neutral (pH 7.0). The neutralized solution is evaporated to dryness upon an atmospheric double drum drier.

EXAMPLE 4 A hydrocarbon fraction boiling from 180 to 300 and obtained from a Pennsylvania crude oil was chlorinated in the presence of catalytic amounts of iodine at a temperature below 60. The chlorination was continued until the specific gravity of the chlorinated hydrocarbon reached 0.92. This corresponds to an average of one and one-quarter atoms of chlorine per molecule of hydrocarbon. 2035 parts of this chlorinated hydrocarbon were rapidly added to a mixture of 1320 parts of benzene and 132 parts of anhydrous aluminum chloride. The mixture was agitated for 5 hours and then allowed to stand overnight. The oil was decanted from the aluminum chloride sludge and washed with an equal volume of water. The unreacted benzene and a part of the unreacted petroleum distillate were removed by distilling up to at 25 mm. pressure. The remaining oil is mainly a mixture of alkyl derivatives of benzene. 400 parts of the resulting mixed alkyl derivatives of benzene were sulfonated with 330 parts of 26 per cent oleum by adding the oleum to the oil at 10, and then agitating at room temperature for two and one-half hours. The mixture was then allowed to stand for about a half hour and the upper layer of unsulfonated material was drawn off. The lower sulfonate layer was then added to parts of ice keeping the temperature below 35 and allowed to stand for about 2 hours, or until residual sulfuric acid separated from the alkyl benzene sulfonic acids. The residual sulfuric, acid was drawn off and the sulfonic acids were then diluted to 20 per cent strength. Basic copper carbonate was added until the product was neutral. The filtered solution was dried. There was thus obtained the copper salt of the mixed alkyl derivatives of benzene sulfonic acid.

In a similar manner, other heavy metal or alkali-metal salts of the alkyl benzene sulfonic acids can be obtained in a form relatively free from inorganic sulfates.

EXAMPLE 5 700 parts of an olefine with a boiling point ranging from 237 to 262 and having an average carbon content of 14 to 15 carbon atoms (and obtained by dechlorination of the monochlor hydrocarbons separated by fractionation from the products resulting from chlorination of petroleum distillates which boil at approximately 250 at atmospheric pressure), 700 parts of phenol, and 350 parts of anhydrous zinc chloride are mixed and heated together while agitated under a reflux condenser at a temperature around to for from 5 to 16 hours. The condensed mass is diluted and washed with water until reasonably free of water-soluble impurities, and the crude brownish-oil is distilled in vacuo. The fraction of the distillate boiling between and 240 at 15 mm. pressure is collected separately. It is a faintly colored to water-white oil, insoluble in water and dilute caustic soda.

100 parts by weight of the resulting oil are,

mixed with 148 parts by weight of sulfuric acid monohydrate at 30, then heated to 70 to 75 and held there until a sample is completely soluble in water and in neutral, acid or alkaline aqueous solutions, and a neutral 0.2 per cent solution does not precipitate calcium salts from a soluble calcium salt solution containing the equivalent of 0.224 gram calcium oxide per liter. The sulfonation mix is poured into water, diluted to a final volume of 450 to 600 parts, and made neutral (for example, to delta paper, Congo red paper, Brilliant yellow, or brom-phenol-blue) with alkali, for example caustic soda, or potash or their equivalents. The neutral solution is evaporated to dryness. If desired, the neutral solution can be clarified by filtration before being evaporated to dryness.

The product thus obtained is a mixture of which the chief components are alkyl phenol sulfonates having the probable formula where Re represents an aliphatic hydrocarbon group, and M represents an alkali metal or equivalent derived from-the base used for neutralization. For the most part, the alkyl phenol sulfonates contain branched carbon chains in the groups represented by Re and these groups are connected to the phenol nucleus by primary, secondary or tertiary carbon atoms. The chief components of the mixture contain 14 or 15 carbon atoms in the alkyl group represented by Re.

In the form of the alkali metal and alkaline earth metal salts it is a faintly colored light brown to white, friable solid, readily reduced to a comminuted or powdery form (resembling powdered soap) and readily soluble in water.

The products of above Examples 2 and 5 contain inorganic salts (e. g., alkali metal sulfates) in admixture with the alkyl aromatic sulfonates. It is preferable to employ the alkyl aromatic sulfonates in a form relatively free from inorganic salts, in which form they may beobtained from the mixed products produced by such processes as are given in said specific examples by taking advantage of the solubility of the alkyl aromatic sulfonate salts in alcohol and other organic solvents. Thus, a mixture of a salt of the sulfonated product and an inorganic sulfate may be extracted with alcohol, and the resulting extract may be evaporated to leave a residue of the purified salt of the sulfonated product. The products are preferably obtained in a form relatively free from inorganic salts by employing chlorsulfonic acid as the sulfonat ng agent or by separating the alkyl aromatic sulfonic acid from residual sulfonating agent by the process described in Example 4.

The following examples illustrate the use of the products herein described. In these exampics, any of the products of Examples 1 to 5 can be employed, which are referred to for convenience as alkyl aryl sulfonate. It will be understood, however, that these examples are merely illustrative and that any of the other sulfonated products herein described may be similarly employed. The parts are in ounces per U. S. A. gallon of electrolyte and temperatures are in degrees Fahrenheit.

Emu 6 Nickel plating-Cold solution (A) A copper plated steel is electroplated in an electrolyte of the following composition:

Parts Nickel sulfate -1 12 Nickel ammonium sulfate 4 Ammonium chloride 3 Boric acid- 3 Alkyl aryl sulfonate 0.1-0.25

Temp. -85"; current density (0. D.)' 545 amps/sq. ft.; voltage 1 -3 volts.

Nickel plating-Hot solution Parts (B) Nickel sulfate 32 Nickel chloride 9 Boric acid 4 I Alkyl aryl sulfonate (Ll-0.25

Temp. -150"; C. D. 30-50 amps/sq. ft.; voltage 3-3.5 volts.

The resulting plaitings are whiter than those obtained in the absence of the akyl aryl sulfonates, and pitting and pin holes are absent.

Similar improved results are secured with other electrolytes in the plating of other metals. A number of suitable electroplating baths are given in the following examples.

Exmm 7 Cadmium plating Parts Cadmium oxide 3 Sodium cy 13 Alkyl aryl sulfonate 0.1-.25

Temp. 70-100"; 0. D. 10-15 amps/sq. ft.; voltage 2-2.5 volts.

EXAMPLE 8 Chromium plating Parts Chromic acid 33 Sulfuric acid .3

Alkyl aryl sulfonate 0.1-.4

Temp. 115"; C. D. amps/sq. ft.; voltage 6-8 volts.

EXAMPLE 9 Copper plating Parts Copper cy 3.0 Sodium cya 4.5 Sodium carbonate 2.0

Alkyl aryl sulfonate 0.1-.25

Temp. 75-100; C. D. 2.5-5 amps/sq. ft.; voltage 1.5-2 volts.

EXAMPLE 10 Gold plating Parts Sodium gold cyanide 0.5 Sodium cyanide 0.5-1.0 Disodium phosphate 2.0 Alkyl aryl sulfonate 0.1-0.2

Temp. 140-160; C. D. 1-5 amps/sq. ft.; voltase 2.5 volts.

Exam: 11

Iron plating Parts Ferrous chloride 40 Calcium chlorlde 25 Alkyl aryl sulfonate 0.10.25

Temp. 185-210"; C. D. 50-100 ampa/sq. ft.; voltage 3-4 volts.

Exmu: 12

Lead platinfl Parts Basic lead carbonate 20 Hydrofluoric acid (50%) 32 Boric a 14 Alkyl aryl sulfonate 0.1-0.25

Temp. 65-85; C. D. 10-20 amps/so. ft.; voltage 3-4volts.

Exnlru: 13

Silver plating (bright deposits) Parts Silver cya 3.5 Potassium cyanide 6.5

(Or sodium cyanide 5.0 parts.) Potassium carbonate 5.0

(0r sodium carbonate 5.0 parts.) Alkyl aryl sulfnnate 0.1-0.25

Temp. 65-75"; C. D. 3-5 amps/sq. ft.; voltage %-1 volt.

Exurru: 14

Tin plating Parts Sodium stannate 24 Caustic soda 1 Sodium acetate 2 Alkyl aryl sulfonate 0.1-0.25

Temp. -170; C. D. 25 amps/sq. ft.; voltage 3-5 volts.

EXAMPLE 15 Zinc plating (0) Acid zinc: Parts Zinc sulfate 32 Sodium acetate 2 Aluminum sulfate 4 Alkyl aryl sulfonate 0.1-0.25

Temp 75-85 C. D. 15-30 amps/sq. ft.; voltage 2-4 volts.

Alkyl aryl sulfonate 0.1-0.25

Temp. 75-85; C. D. 10-37 amps/sq. ft.; voltage b-3V2 volts.

Parts (12) Cobalt sulfate (anhyd) 37 Sodium chloride 2.3 Boric acid 6.0 Alkyl aryl sulfonate 0.1-0.25

Temp. IO-80; C. D. 33-160 amps/sq. ft.; voltage 2-4 volts.

It will be realized by those skilled in the art that changes may be made in the process of electroplating and in the composition of the electrolytes without departing from the invention. The alkyl aromatic sulfonates employed in accordance with the present invention have the advantage t being stable in acid, alkaline and neutral baths, even in hot acid plating baths, and of forming salts with a number of heavy metals employed in electroplating which salts are soluble in water, whereby they may be used in a wide variety of electrodepositing processes and under a variety of conditions.

I claim:

1. In the process of electrodepositing metals the improvement which comprises electrolyzing an aqueous solution containing the metal to be deposited and an alkyl aromatic sulfonic acid compound of the benzene series containing at least '7 carbon atoms in an alkyl group.

2. In the process of electrodepositing metals the improvement which comprises electrolyzing an aqueous solution containing the metal to be deposited and an alkyl aromatic sulfonate of the benzene series containing 7 to 35 carbon atoms in an open-chain aliphatic hydrocarbon radical.

3, In the process of electrodepositing metals, the improvement which comprises electrolyzing an aqueous solution containing a metal selected from the group consisting of nickel, cadmium, chromium, copper, gold, iron, lead, silver, tin, zinc and cobalt, and an alkyl aromatic sulfonic acid compound of the benzene series containing at least 7 carbon atoms in an alkyl group.

4. In the process of electrodepositing metals the improvement which comprises electrolyzing an aqueous solution containing the metal to be deposited and an alkyl aromatic sulfonate of the benzene series containing at least 10 carbon atoms in an alkyl group.

5. In the process of electrodepositing metals, the improvement which comprises electrolyzing an aqueous solution containing a metal selected from the group consisting of nickel, cadmium, chromium, copper, gold, iron, lead, silver, tin, zinc and cobalt, and an alkyl aromatic sulfonate of the benzene series containing at least 10 carbon atoms in an alkyl group.

6. In the process of electrodepositing metals the improvement which comprises electrolyzing an aqueous solution containing the metal to be deposited and an alkyl aromatic sulfonate of the benzene series containing 10 to 19 carbon atoms in an open-chain aliphatic hydrocarbon radical.

7. In the process of electrodepositing metals, the improvement which comprises electrolyzing an aqueous solution containing the metalto be deposited and a mixture of alkyl aromatic sulfonates of the benzene series each containing at least 7 carbon atoms in an alkyl group which is derived from a petroleum hydrocarbon.

8. In the process of electrodepositing metals, the improvement which comprises electrolyzing an aqueous solution containing the metal to be deposited and a mixture of alkyl aromatic sulfonates of the benzene series each containing at least 10 carbon atoms in a branched carbon chain which is derived from a petroleum hydrocarbon.

9. In the process of electrodepositing metals, the improvement which comprises electrolyzing an aqueous solution containing the metal to be deposited and a mixture of alkyl aromatic sulfonates of the benzene series each containing 10 to 19 carbon atoms in an alkyl group which is derived from a petroleum hydrocarbon.

10. In the process of electrodepositing metals, the improvement which comprises electrolyzing an aqueous solution containing the metal to be deposited and a mixture of alkyl aromatic sulfonates of the benzene series in which the alkyl groups correspond, with aliphatic hydrocarbons of petroleum distillates boiling above 170 0., and which are obtainable by halogenation of the petroleum distillate, condensation of resultin mixed alkyl halides with an aromatic hydrocarbon of the benzene series, and sulfonation of resulting mixed alkyl benzenes.

11. In the process of electrodepositing metals, the improvement which comprises electrolyzing an aqueous solution containing the metal to be deposited and an alkyl benzene sulfonate containing at least 7 carbon atoms in an alkyl group.

12. In the process of electrodepositing metals, the improvement which comprises electrolyzing an aqueous solution, containing the metal to be deposited and an alkyl benzene sulfonate containing at least 10 carbon atoms in an alkyl group.

13. In the process of electrodepositing metals, the improvement which comprises electrolyzing an aqueous solution containing the metal to be deposited and an alkylbenzene sulfonate containing 10 to 19 carbon atoms in an open-chain aliphatic hydrocarbon radical.

14. An electroplating bath comprising an aqueous solution of a compound of the metal to be deposited by electrolysis and an alkyl aromatic sulfonate of the benzene series containing at least 7 carbon atoms in an alkyl group.

15. An electroplating bath comprising an aqueous solution of a compound of the metal to be deposited by electrolysis and an alkyl aromatic sulfonate of the benzene series containing at least 10 carbon atoms in an alkyl group.

16. An electroplating bath comprising an aqueous solution of a compound of the metal to be deposited by electrolysis and an alkyl aromatic sulfonate of the benzene series containing 10 to 19 carbon atoms in an open-chain aliphatic hydrocarbon radical.

1'7. In the process of electrodepositing metals, the improvement which comprises electrolyzing an aqueous solution containing a metal selected from the group consisting of nickel, cadmium, chromium, copper, gold, iron, lead, silver, tin, zinc and cobalt, and an alkyl benzene sulfonate containing 10 to 19 carbon atoms in an openchain aliphatic hydrocarbon radical.

18. In the process of electrodepositing metals, the improvement which comprises electrolyzing an aqueous solution containing a metal selected from the group consisting of nickel, cadmium, chromium, copper, gold, iron, lead, silver, tin, zinc and cobalt, and a mixture of alkyl aromatic sulfonates of the benzene series each containing 10 to 19 carbon atoms in an alkyl group which is derived from a petroleum hydrocarbon.

19. In the process of electrodepositing metals, the improvement which comprises electrolyzing an aqueous solution containing a metal selected from the group consisting of nickel, cadmium, chromium, copper, gold, iron, lead, silver, tin, zinc and cobalt, and a mixture of alkyl aromatic sulfonates of the benzene series in which the alkyl groups correspond with aliphatic hydrocarbons of petroleum distillates boiling above 170 C., and which are obtainable by halogenation of the petroleum distillate, condensation of resulting mixed alkyl halides with an aromatic hydrocarbon of the benzene series, and suli'onation of resulting mixed alkyl benzenes.

20. In the process of electrodepositing metals, the improvement which comprises electrolyzing an aqueous solution containing nickel and an alkyl aromatic suli'onate of the benzene series containing at least '7 carbon atoms in an alkyl up.

21. In the process of electrodepositing metals, the improvement which comprises electrolyzing an aqueous solution containing nickel and an alkyl aromatic sulfonate of the benzene series containing at least 10 carbon atoms in an alkyl group.

22. In the process of electrodepositing metals. the improvement which comprises electrolyzing an aqueous solution containing nickel, and an alkyl benzene sulfonate containing 10 to 19 carbon atoms in an open chain aliphatic hydrocarbon radical.

23. In the process of electrodepositing metals, the improvement which comprises eiectrolyzing an aqueous solution containing nickel and a mixture of alkyl aromatic sulfonates of the benzene series in which the alkyl groups correspond with aliphatic hydrocarbons of petroleum distillates boiling above 170 0., and which are obtainable by halogenation of the petroleum distillate. condensation of resulting mixed alkyl halides with an aromatic hydrocarbon of the benzene series, and sultonation of resulting mixed allgvl benzenes.

LAWRENCE H. FLE'I'I'. 

